Various wired and wireless communication systems deploy transceivers which may use any spectrally efficient modulation scheme, such as Quadrature Amplitude Modulation (“QAM”). A channel adaptive communication system, including a transceiver, conventionally has a transmitter at one end and a receiver at another end, which communicate with each other via a communication channel. Notably, as used herein “include” and “including” mean “including without limitation. The transmitter modulates information onto a carrier signal. The modulated signal propagates to the receiver via the communication channel. The communication channel may be free space, such as a wireless channel, or confined, such as a wired channel. The receiver demodulates the information transmitted via the channel. However, multiple reflections in the communication channel may distort the transmission path in the channel and deform the signal due to an inter-symbol interference (“ISI”). The distortion caused by ISI is conventionally removed before the signal is demodulated by the receiver.
Conventionally, a pre-equalizer is used to adjust the transmitter to channel distortion to remove ISI. A transmitter may transmit a preamble set of information via a communication channel before transmitting the actually data payload. A receiver may use a channel estimator to evaluate a frequency response of the communication channel via the preamble set of information received. The estimator provides the inverse communication channel frequency response which is sent from the receiver to the pre-equalizer of the transmitter. The pre-equalizer applies the inverse channel frequency response to subsequently transmitted signals, which eliminates ISI distortion introduced by the communication channel.
Conventionally, both a transmitter and a receiver are included in a single transceiver integrated circuit, and thus dedicated transceiver circuitry is used for removal of ISI. Dedicated equalizer hardware learns the channel frequency response and evolves a set of correction coefficients which are inversely applied to a signal to correct ISI distortion. Dedicated circuitry (“hardware”) responsible for adaptively equalizing ISI distortion conventionally resides in the receiver. This dedicated adaptive equalization circuitry remains in the hardware, even if the communication channel is stabilized over time, such as in cable television systems. The ever present adaptive equalization circuitry consumes power and adds cost.
Accordingly, it would be both desirable and useful to provide an adaptive communication system without one or more of the above-mentioned limitations.